Rivet fastener with drilling bit

ABSTRACT

A rivet fastener includes a threaded spindle having at a free end thereof a drill bit and an external casing having a stop flange and a sleeve portion with an internal thread corresponding to that of the spindle and receiving the spindle. The casing has a plurality of set-breaking grooves extending parallel to the axis of the casing. The threads and the drill bit are formed such that the threads run in a direction opposite to that of a drilling rotation.

BACKGROUND OF THE INVENTION

The present invention pertains to a rivet fastener connection assemblyconsisting of a rivet casing and a rivet spindle employable in the rivetcasing. The spindle has a bolt-shaped shaft and, a larger head unitcompared to the diameter of the shaft, and the head unit is formed orset onto said shaft. A drilling unit is formed or set onto the headunit, where the rivet casing and has an inner thread over at least apart of its length, and the shaft of the rivet spindle has an outerthread corresponding to the inner thread, over at least a part of itslength, and wherein means are provided on the rivet casing and/or on acontact flange formed on the rivet casing, for form- and/or force-fittedmount of the rivet casing against the workpiece to be riveted, and/oragainst a setting tool for the rivet connector.

This type of a rivet connector is known from DE-OS 17 75 430 or fromU.S. Pat. No. 3,453,927. This rivet connector does not generate a rivetconnection by pulling the rivet spindle out in an axial direction afterinserting the rivet connector into a drilled hole in the workpiece, inorder to deform the rearward, free end of the rivet casing by thisprocess, but rather, it concerns a means of effecting the rivetingitself by turning the rivet spindle. In this case, the rivet casing hasan inner thread and the rivet spindle has an outer thread correspondingto the inner thread, and the tensile force to deform the free end of therivet casing is exerted on the head unit by twisting the rivet spindlein the rivet casing. In this case, very strong friction forces will begenerated since a deformation of the free end of the rivet casing willoccur. Thus in this known rivet connector the rivet spindle will oftenbreak (for example, at a set breakpoint), so that the setting process ofthe rivet connection cannot be terminated at all.

DE 32 17 065 A1 discloses a method to gap-open the free-end region ofthe rivet casing of pull-rivets, where the pull spindle is pulled outonly in an axial direction. Due to the special formation of the headunit on the pull spindle, a tear-off of the free end of the rivet casingis effected by pyramid-shaped beveling, whereupon the pyramid edgesnotch in the rivet casing, so that the rivet casing tears open axiallywhen tightening the head. This type of the connector can only be used onpure pull-spindles, since these tear-open edges on the pull spindlewould prevent a twist motion of the pull spindle against the rivethousing. In addition, when meshing with the rivet casing, the edgeswould immediately cause such a large rise in the torque that the rivetcasing would also turn or twist in a radial direction. An orderlysetting process thus could not be implemented.

From DE-AS 14 75 216 a rivet connector is known where the rivet casingis equipped with an inner thread and the rivet spindle is provided in anouter thread, so that by turning motion of the rivet spindle, theriveting can be completed. In this known rivet connection there areproblems however, inasmuch as the turning of the rivet casing duringtightening of the rivet spindle cannot be prevented, so that not onlycould the workpiece be damaged, but also the rivet itself will notsufficiently ensure reliability.

From DE-OS 19 63 526 a self-drilling blind rivet is known that has athickened section at the region adjoining the head unit of the shaft ofthe rivet spindle, whereby a thread is cut into this thickening. Thisthickened section with thread has a diameter that is much larger thanthat of the rivet spindle itself, and during the setting process,through rapid tightening of the rivet spindle with this threaded region,an expansion of the rivet casing will be effected. Since the advance ofthe pull part is much larger for this rivet spindle than the threadpitch on the rivet spindle, this threaded section on the rivet spindlewill merely be contracted into the rivet casing, without requiring anopposing thread to be formed in the rivet casing. Thus only the insidediameter of the rivet casing will be expanded, so that it will pressagainst the wall of the drilled hole in the workpiece.

Finally, DE 32 46 625 A1 and from DE 35 42 581 A1, rivet connectorswithout a drill section are known, where the rivet casing is notdeformed during the setting procedure, but rather the diameter of anadditional casing located over the rivet spindle is expanded by means ofthe rivet casing.

SUMMARY OF THE INVENTION

An object of the invention is to create a solid rivet connection unitwith a rivet connection of the type described above, used without thenecessity of a torque having a negative effect on setting process to beapplied on the unit.

This and other objects of the invention are attained by a rivetconnector which has a rivet casing with at least one predeterminedbreaking line running at least approximately parallel to the axis over apart of its length, beginning from the end turned away from the contactflange.

Since the rivet connector of this invention has a rivet spindle and alsoa head unit that turns opposite the fixed rivet casing during thesetting process, the first axial force application to the free end ofthe rivet casing, due to the predetermined breaking lines, will splitthis region open so that the single-sector sections of the rivet casingwill bend outward. Only when there is practically just the material ofthe thick, sector-like sections of the rivet casing still presentbetween the underside of the workpiece and the head unit, will thetorque for further twisting of the rivet spindle increase, so that atthe final stage of the setting process, a sudden increase in torque willoccur, leading to an optimum conclusion of the setting process.

In the rivet connector according to this invention, when tightening therivet spindle, the free end of the rivet casing tears open at thelocations defined by the predetermined breaking lines, so that singletabs separate from each other and are pressed outward. This will causenot only a very good rivet connection, but also the force application togenerate this rivet connection is also reduced considerably. This is animportant advantage over the known rivet connection unit in which therivet casing is merely deformed axially or has its diameter expanded.

The type and manner of forming the predetermined breaking lines in therivet casing has a particularly favorable effect on the subsequentsetting, or the rivet connection. It is particularly useful that thepredetermined breaking lines of the rivet casing be formed as notches,grooves or slits running parallel to the axis. This will create not onlya simple separation of the single sections at the perimeter region ofthe rivet casing, but it will also ensure that practically star-shapedperimeter sections of equal size will always be bent outward. It is anadvantage if the predetermined breaking lines are formed in the form ofnotches or grooves at the inner and/or at the outer wall of the rivetcasing. The notches or grooves are of triangular, polygonal, trapezoidalor circular cross section. It is expedient to provide at least threesequential predetermined breaking lines distributed uniformly along theperimeter of the rivet casing.

Another possibility for satisfactory tear-open of the end region of therivet casing during the setting process resides in the fact that at thefree end of the rivet casing, radial slits, notches or grooves can beformed that run all the way through and are open toward the end of therivet casing. Thus set-break notches are created practically at the freeend of the rivet casing, so that an orderly tear-open can occur, perhapswith no additional predetermined breaking lines running in an axialdirection.

In this regard it is also possible that the notches or grooves of thepredetermined breaking lines pass into slits, notches or grooves runningradially at the free end of the rivet casing. This is then a combinationof predetermined breaking lines running in an axial direction, with theradial slits, notches or grooves running all the way through.

For an optimal deformation of the rivet casing and a simpler in and outpressing of the free end of the rivet casing, it is an advantage if ablunt cone-shaped transition portion is provided between the shaft andthe head unit of the rivet spindle.

Preferred embodiments of the invention will be described in greaterdetail below, with reference to the figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side sectional view of a rivet connector

FIG. 2 is a side view of the rivet connector;

FIG. 3 is a top view of the rivet connector;

FIG. 4 is a side sectional view of another embodiment

FIG. 5 is a side sectional view of the rivet connector after completionof the setting process on one workpiece;

FIG. 6 is a top view of the rivet connector according to FIG. 4;

FIG. 7 is a cross section view through a rivet casing according to FIG.4;

FIG. 8 is a top view of the rivet casing;

FIG. 9 is a cross section view through the rivet casing in the region ofthe predetermined breaking lines;

FIG. 10 is a side view of the rivet spindle of the rivet connectionaccording to FIG. 4; and

FIG. 11 is a top view of the rivet spindle according to FIG. 10;

FIG. 12 is a cross-sectional view through the rivet casing havingpredetermined breaking grooves in the outer wall thereof;

FIG. 13 is a cross-sectional elevation view of the rivet casing of FIG.12 with the rivet spindle inserted therein;

FIG. 14 is a cross-sectional view similar to that of FIG. 9 but with thecasing having triangular grooves;

FIG. 15 is a cross-sectional view similar to that of FIG. 14 but withcircular grooves; and

FIG. 16 is a cross-sectional view similar to that of FIG. 15 but withthe grooves formed as slits.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The rivet connector consists essentially of a rivet casing (1) and arivet spindle (2). The rivet spindle (2) is composed of a bolt-shapedshaft (3) and a head unit (4) of a larger diameter than that of theshaft and located or shaped on this shaft. The rivet casing (1) isprovided with an inner thread (5) which is produced before or during thesetting process. Shaft (3) of the rivet spindle (2) is provided with acorresponding outer thread (6). One or several protruding ribs,expansions, grooves, roughenings, slits, flattenings or similar featuresfor form- and/or force-fitted mounting of rivet casing (1) formed on thecontact flange (7) formed on the rivet casing (1) are provided oppositethe workpiece to be riveted and/or opposite a setting tool for the rivetconnector.

The rivet connector can be introduced into a prepared opening in aworkpiece and then set. In the illustrated embodiments, a drill or bitpiece (8) is provided or formed on the head unit (4). In the embodimentsof for FIGS. 1-3, piece 8 is a plate-shaped cut-piece and in theembodiment of FIGS. 4, 5 and 10, it is a drill piece of a circular crosssection.

The direction of the hole drilling and the rotation direction whentightening the rivet spindle (2) are the same, and the inner thread (5)at the rivet casing (1) and the outer thread (6) on shaft (3) runopposite the direction of turning when drilling the hole, so that for adrill rotation directed in a clockwise direction, a left thread on shaft(3) and on rivet casing (1) will be used.

In the embodiment of FIGS. 1-3, the inner thread (5) of the rivet casing(1) runs only along a partial region of its length, but the, lower freeend of the rivet casing (1) forms a cylindrical casing on the inside.Shaft (3) of rivet spindle (2) is provided along its entire length withan outer thread (6). On the free-end region of rivet spindle (2), aninner or outer drive unit is provided for insertion or application of atool. In the embodiment shown in FIGS. 1-3, at the free end of the rivetspindle (2) there are bevels (9) located at diametrically opposingregions. In this design, the rivet spindle (2) is longer than the rivetcasing (1) and in the region of shaft (3) located within the rivetcasing (1), a set-break point (10) is provided.

Between shaft (3) and head unit (4) of the rivet spindle (2) there is ablunt cone-shaped transition section (11) which simplifies the settingprocess, that is, the pull-in of the head unit (4) into the rivet casing(1).

At the free end of the rivet casing (1), there are radial slits (12)extending all the way through and open on the end of the casing. Due tothese slits (12), when the head unit (4) of the rivet spindle (2) isinserted, the free-end region of the rivet casing (1) will tear open.This then will create set-break notches.

In the embodiment according to FIGS. 1-3 there is a conical expansion(13) enlarged toward the contact flange located at the transitionbetween the rivet casing (1) and the contact flange (7) at the outersurface of rivet casing (1). This expansion allows a force-fit mount ofthe rivet casing (1) in the drilled hole of the workpiece. Afterdrilling through the workpiece and a corresponding, forced insertion ofthe rivet casing (1) into the drilled hole, for example, by a hammerimpact, a fixed seat of the rivet casing (1) is ensured with respect tothe workpiece. In this design, the potential is created that the rivetcasing (1) can be secured against twisting during the setting processusing a setting tool or an appropriate hand tool. With this design, twodiametrically opposing bevels (14) can be provided as tool applicationsurfaces on the contact flange (7). The contact flange (7) of the rivetcasing (1) could also be equipped with a unit like a screw head, withtool application surface and/or slits.

With this embodiment it would also be possible to employ an additionalseal and also an O-ring for additional twist-lock, since acircumferential ring groove (15) is formed on the underside of thecontact flange (7). At the underside of contact flange (7), afriction-enhancing washer could also be used, e.g., a rubber washer. Ifit is merely important to secure the rivet casing (1) against twisting,then a toothed disk could also be used at the underside of the contactflange (7).

In the embodiment according to FIGS. 4-11, the rivet casing (1) isprovided along its entire length with an inner thread (5). Shaft (3) ofthe rivet spindle (2) is shorter than the length of rivet casing (1) andon its free end it has an internal drive unit (16). In this embodiment,the pull-spindle (2) does not extend over the surface of the rivetcasing (1), not even after final setting of the rivet connection, sothat no set-break points are required here. Thus no parts will be lostand no parts will drop off.

In this embodiment the rivet casing (1) has predetermined breaking lines(17) running at least approximately parallel to the axis along a part ofits length, beginning from the end turned away from the contact flange(7). These predetermined breaking lines (17) are formed by notches orgrooves at the inside wall of rivet casing (1), but could also bedesigned in the form of radial slits running all the way through asshown in FIGS. 12 and 13. But it would also be possible to form thesepredetermined breaking lines (17) at the outer wall of rivet casing (1),or alternately at the inside and outside wall. The cross-sectional shapeof the predetermined breaking lines (17) can be selected differently. Itis therefore possible to form the notches or grooves in a triangular,polygonal, trapezoidal, or circular cross section. Trapezoidal-shapedgrooves are shown in FIG. 9, triangular-shaped grooves are shown in FIG.14 and the grooves of a circular cross-section are shown in FIG. 15.FIG. 16 shows the grooves of slit shape. At any rate, it is an advantageif at least three sequential predetermined breaking lines (17) aredistributed uniformly around the perimeter of casing (1). According toFIG. 5, the circumferential sections of the rivet casing (1) will bepressed apart in a star-shape by the predetermined breaking lines (17),so that an optimum locking of the rivet casing (1) will occur at theback side of a workpiece (18) being riveted.

In this regard it would also be possible to combine the embodimentaccording to FIG. 1 and FIG. 4 so that then the notches or grooves ofthe predetermined breaking lines (17) will pass into radial slits (12)running all the way through at the free end of the rivet casing (1).Then the tear-off of the rivet casing (1) would also be improved in theregion of the predetermined breaking lines (17).

For setting a rivet connector according to the above description, itwill first be inserted onto the workpiece (18), and the drilling bit (8)will produce the drilled hole in workpiece (18). Due to the specialformation of the thread, the rivet spindle (2) can be pulled into therivet casing (1) upon additional turning of the rivet spindle in thesame direction of rotation used in the drilling process, so thatsubsequently an orderly riveting is achieved.

In the description and in the figures, self-drilled rivet connectors areillustrated and explained. But rivet connectors can also be used thatare inserted into predrilled holes on workpiece (18). Then merely thedrilling unit (8) of the rivet spindle (2) will be eliminated.

To secure the rivet casing (1) against turning with respect to workpiece(18) or with respect to a setting tool, various design configurationsare possible. It would be possible for example, to install one or moreradially protruding ribs or hubs aligned parallel with the axisunderneath the contact flange (7) on the rivet casing (1). Anothersample embodiment is to form the contact flange (7) of the rivet casing(1) as a recessed head with a multi-cornered cross section. It wouldalso be possible for the outer region of the rivet casing (1) to have aknurling, ridging or roughening at least in the region directlyadjoining the contact flange (7), in order thereby to achieve a force-and/or form-fitted mount of rivet casing (1) in the drilled hole ofworkpiece (18). Another variant would be to provide a gearing withradially running teeth or ribs at the underside of the contact flange(7).

The predetermined breaking lines (17) in the embodiments shown in FIGS.4 and 7 run along about two-thirds of the length of the rivet casing (1)proceeding from their free end-region. This length is variable,depending on the purpose of the rivet casing (1) or the rivetconnection.

In the described embodiments the rivet casing (1) comes into directcontact with the head unit (4) of the rivet spindle (2). A design wouldbe possible where a casing is inserted between the free end of the rivetcasing (1) and the head unit (4) of the rivet spindle (2) and thiscasing is deformable when tightening the rivet connection. A casing madeof rubber, plastic or aluminum could be used in the connector of theinvention.

A material is selected for the rivet spindle (2) and the rivet casing(1) which is an optimal material for the particular end use. So it ispossible to produce the rivet casing (1) of metal or even out ofplastic. One such version would be of particular interest if the rivetcasing (1) were to have an insulating function.

What is claimed is:
 1. A self-drilling rivet fastener, comprising arivet casing and a rivet spindle inserted into said rivet casing, saidrivet casing having an internal thread extending over at least a part ofa length thereof and including a sleeve portion and a stop flange of alarger diameter, said rivet spindle including a bolt-shaped shaft havingan external thread over at least a part of a length thereof andcorresponding to said internal thread and adapted for threadingthereinto and a head unit terminating with a drill bit for producing ahole in a workpiece for receiving the fastener, said internal andexternal threads being formed such that rotation of said rivet spindleto produce a hole in the workpiece will cause said rivet spindle tothread into said sleeve portion to set the rivet, said flange havingshaped surface means on a face thereof facing the workpiece to provide afitting mount of said rivet casing against the workpiece, said rivetcasing being formed with predetermined breaking grooves extendingparallel to an axis of the casing over a part of the length thereofstarting at said stop flange.
 2. The fastener according to claim 1,wherein said grooves are slit-shaped.
 3. The fastener according to claim1, wherein said grooves are formed in an inner wall of said casing. 4.The fastener according to claim 1, wherein said grooves are oftrapezoidal cross-section.
 5. The fastener according to claim 1, whereinsaid grooves are of triangular cross-section.
 6. The fastener accordingto claim 1, wherein said grooves are of circular cross-section.
 7. Thefastener according to claim 1, wherein said grooves are formed in anouter wall of said casing.
 8. The fastener according to claim 1, whereinat least three of said grooves are formed.
 9. The fastener according toclaim 1, wherein said casing has a free end which is formed with radialslits open to said end of said casing.
 10. The fastener according toclaim 9, wherein said grooves merge into said radial slits.
 11. Thefastener according to claim 1, wherein said spindle includes afrustoconical transition portion between said shaft and said head unit.12. A self drilling rivet fastener, comprising a rivet casing and arivet spindle inserted into said rivet casing, said rivet casing havingan internal thread extending over at least a part of a length thereofand including a sleeve portion and a stop flange of a larger diameter,said rivet spindle including a bolt-shaped shaft having an externalthread over at least a part of a length thereof and corresponding tosaid internal thread and adapted for threading thereinto and a head unitterminating with a drill bit for producing a hole in a workpiece forreceiving the fastener, said internal and external threads being formedsuch that rotation of said rivet spindle to produce a hole in theworkpiece will cause said rivet spindle to thread into said sleeveportion to set the rivet, said flange having shaped surface means on aface thereof facing the workpiece to provide a fitting mount of saidrivet casing against the workpiece, said rivet casing being formed withpredetermined breaking grooves extending parallel to an axis of thecasing over a part of the length thereof starting at said stop flange,said rivet casing further including radially extending slits at a freeend thereof, said grooves merging into said radially extending slits.13. The fastener according to claim 12, wherein said grooves areslit-shaped.
 14. The fastener according to claim 12, wherein saidgrooves are formed in an inner wall of said casing.
 15. The fasteneraccording to claim 12, wherein said grooves are of trapezoidalcross-section.
 16. The fastener according to claim 12, wherein saidgrooves are of triangular cross-section.
 17. The fastener according toclaim 12, wherein said grooves are of circular cross-section.
 18. Thefastener according to claim 12, wherein said grooves are formed in anouter wall of said casing.
 19. The fastener according to claim 12,wherein at least three of said grooves are formed.
 20. The fasteneraccording to claim 12, wherein said spindle includes a frustoconicaltransition portion between said shaft and said head unit.